A stent is a small mesh tube that is used to treat narrowed or weak lumens (e.g., an artery, vein, bile duct, esophagus, intestine, lung, etc.), for example, to counteract lumen constriction due to various diseases and conditions. Stents can be formed from metals, polymers or other suitable material. Stents can be biostable or bioresorbable, drug eluting or non-drug-eluting. The most common use for a stent is in coronary arteries. Other common types of stents besides coronary stents include peripheral stents, ureteral stents (e.g., to ensure patency of the ureter), biliary stents (e.g., to treat obstruction in the bile or pancreatic duct), esophageal stents (e.g., to treat blockages of the esophagus), enteral stents (e.g., to treat blockage of the small bowel or colon), and airway stents (e.g., to treat blockage of the trachea or bronchi), among others.
In some cases, stents are covered. If the covering of the covered stent is porous, typically for use in the vasculature, it is often called a stent-graft. Stent-grafts are used in the treatment of abdominal aortic aneurysms and weakened peripheral arteries. Other covered stents may be used for the treatment of malignant or benign strictures of the esophagus as well leaks and/or perforations in various body lumens, among other uses. In some cases covered stents are temporarily placed and are removable.
Fixation is extremely important in the placement of a stent, whether covered, partially covered or non-covered, because if the implant migrates, the treatment can be compromised and further complications can occur.
As one specific example, placement of covered self-expanding metal or polymer stents has been the first choice for palliative therapy of unresectable esophageal cancer. These stents are also highly effective for the management of benign (peptic, postsurgical, corrosive) strictures, esophageal leaks, perforations and fistula. In most cases, rapid relief of dysphagia and adequate oral intake of nutrients can be achieved. If the stent migrates from the esophagus, such as into the stomach or small intestine causing an obstruction, the patient can suffer severe pain and fever resulting in an additional surgery to remove the stent. The same also applies for other GI and airway stents.
As another specific example, abdominal aortic aneurysm (AAA) stent-grafts are often used to address arterial aneurysms, which are characterized by a weak artery wall. Over time, blood pressure and other factors can cause this weak area to bulge like a balloon and it can eventually enlarge and rupture. The AAA stent graft is designed to seal tightly with the artery above and below the aneurysm. The graft is stronger than the weakened artery and it allows blood to pass through it without pushing on the bulge. If the stent-graft were to migrate, the seal above the aneurysm may be compromised. This may result in blood flowing into the aneurysmal sac causing it to grow and possible rupture. Re-intervention may be required.